Better bounds checks in ctcloss (#16269)
Summary:
Adds better bounds checks for target lengths in CTC loss, checks for integral types for target and prediction lengths, and adds tests for each, according to #15946
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16269
Differential Revision: D13847567
Pulled By: ezyang
fbshipit-source-id: 5d7a975565e02baf78fe388813a1d1ef56dfb212
